Natural magnets were ground into crude compasses which called “Sinan” (a device pointing the south) as early as in the Warring States Period, and that was the oldest compass in the world, 2 000 years ago from now. The magnetic effect of Sinan was weak, as was its ability to guide south.
司南通常被认为是中国古代辨别方向用的一种仪器。据《古矿录》记载最早出现于战国时期的河北磁山一带。近代考古学家猜测是用天然磁铁矿石琢成一个杓形的东西，放在一个光滑的盘上，盘上刻着方位，利用磁铁指南的作用，可以辨别方向，是现在所用指南针的始祖。但并无完整的考古实物。